1:18 The verb "enlighten" is a perfert verb from "photiz-oo." This tense points toward the fact that at some point we were enlightened. Looking over the first chapter of Ephesians, this seems to be baptism (1.15).
What is interesting though is that Paul then is confessing that they have Christ, but is still praying for them. In this case he is praying for knowledge. Perhaps another way to look at it is that he is praying that they would come to realize the power of their baptism.
1.18 The word "heart" (kardia) comes up here; it is used 6 times in Ephesians to describe the spiritual locus in our body.
[1.18 Grammar note: The infinitive of to know "eidenai" is in used in an articular infinitive phrase with "eis" which denotes purpose. Also the "umas," in the accusative here, is the subject of the infinitive clause]
1.19 The langauge in Greek is "immeasurable" here -- a brutal stacking of nouns that compliment the content (nouns in 18 and 19 have been translated as adjectives just to have the sentence be readible). (The word immeasurable/exceeding is used 3 times in Ephesians; 2x in 2 Cor and that is it in the NT)
1:20 Paul talks here about "God 'energizing' by raising Christ from the dead." In 3.20 we will hear of God's energy for us.
1.22 The NRSV and NIV suggest that Christ is given "head over all things/everything for the church." The NET translates the dative case of the church as "to the church." Both are grammatically possible. However, I find it odd to think that God would give the head to the body instead of for the body.